Arrays of probes are often employed for electronic part testing, especially in connection with integrated circuit (IC) chips. Progress in IC chip technology tends to entail an increased number of contacts per IC chip and/or a decrease in the spacing between chip contacts. This spacing is known as the pitch of the contacts. A relatively recent development in IC technology is the use of chip contacts that are arranged in a fine-pitch densely packed 2-D array. FIG. 1 shows an example of such a contact array 104 on a chip 102. Previously, chip contacts have usually been arranged as linear arrays of contacts (i.e., 1-D arrays that are not densely packed in two dimensions).
This change from 1-D to 2-D arrays of chip contacts has significant implications for probe design, and approaches that are suitable for a 1-D contact array are generally unsuitable for use with 2-D arrays. An example of the difficulties that can arise in such cases is shown on FIG. 2. In this example, a vertical probe 204 has a flexure section 206 and passes through a guide plate 202 to control the position of the probe tip (at bottom of figure). Extending the probe concept of FIG. 2 to a 1-D array of contacts has been done. For a 1-D probe array, it is possible to arrange the probes such that the flexure section 206 of each probe has room to move during operation without shorting to another probe. Such 1-D probe arrays can have fine pitch (i.e., 100 μm or less) between adjacent probes without shorting.
However, it is typically not possible to arrange probes as shown on FIG. 2 in a fine pitch, densely-packed 2-D probe array without encountering insuperable probe shorting issues. This problem is further exacerbated by deformation of probes during normal operation of the probe array (i.e., the contact force between probes and chip is usually sufficient to elastically deform the probes). Thus, even if a non-shorting arrangement of probes is possible when the probes are not deformed, it is likely that probe deformation during use will lead to shorts.
Accordingly, it would be an advance in the art to provide probe arrays suitable for probing densely packed, fine-pitch 2-D contact arrays.